print("Please input two numbers")
print("Or you can print 'q' to quit")

while True:
    first_number=input('\nFirst number =')
    if first_number=='q':
        break
    second_number=input('Seconde number =')
    if second_number=='q':
        break
    try:
        plus_number=int(first_number)+int(second_number)
    except ValueError:
        print("Error input ! Please re-enter valid numbers")
    else:
        print(plus_number)